Wnt/β-catenin signaling pathway induces autophagy-mediated temozolomide-resistance in human glioblastoma

Temozolomide (TMZ) is widely used for treating glioblastoma multiforme (GBM), however, the treatment of such brain tumors remains a challenge due to the development of resistance. Increasing studies have found that TMZ treatment could induce autophagy that may link to therapeutic resistance in GBM, but, the precise mechanisms are not fully understood. Understanding the molecular mechanisms underlying the response of GBM to chemotherapy is paramount for developing improved cancer therapeutics. In this study, we demonstrated that the loss of DOC-2/DAB2 interacting protein (DAB2IP) is responsible for TMZ-resistance in GBM through ATG9B. DAB2IP sensitized GBM to TMZ and suppressed TMZ-induced autophagy by negatively regulating ATG9B expression. A higher level of ATG9B expression was associated with GBM compared to low-grade glioma. The knockdown of ATG9B expression in GBM cells suppressed TMZ-induced autophagy as well as TMZ-resistance. Furthermore, we showed that DAB2IP negatively regulated ATG9B expression by blocking the Wnt/β-catenin pathway. To enhance the benefit of TMZ and avoid therapeutic resistance, effective combination strategies were tested using a small molecule inhibitor blocking the Wnt/β-catenin pathway in addition to TMZ. The combination treatment synergistically enhanced the efficacy of TMZ in GBM cells. In conclusion, the present study identified the mechanisms of TMZ-resistance of GBM mediated by DAB2IP and ATG9B which provides insight into a potential strategy to overcome TMZ chemo-resistance.